.TH HRFFT 1 "16 June 2003" "WFDB 10.3.8" "WFDB Applications Guide"
.SH NAME
hrfft, hrlomb, hrmem \- calculate and plot heart rate power spectra
.br
hrplot \- plot heart rate time series
.SH SYNOPSIS
\fBhrfft\fR [ \fIoptions ...\fR ]
.br
\fBhrlomb\fR [ \fIoptions ...\fR ]
.br
\fBhrmem\fR [ \fIoptions ...\fR ]
.br
\fBhrplot\fR [ \fIoptions ...\fR ]
.SH DESCRIPTION
.PP
The first three of these UNIX shell scripts are intended to illustrate the use
of \fBfft\fR(1), \fBlomb\fR(1), and \fBmemse\fR(1) by producing heart rate
power spectra using the fast Fourier transform, the Lomb periodogram,
and the maximum entropy (all poles) method (also known as autoregressive,
or AR, power spectral density estimation).  All four programs derive heart
rate time series from beat annotation files.  \fBhrfft\fR and \fBhrmem\fR use
\fBtach\fR(1) to obtain a uniformly resampled heart rate time series from the
annotation file, which is then used as input to \fBfft\fR or \fBmemse\fR,
and the spectrum thereby obtained is then plotted.  \fBhrlomb\fR and
\fBhrplot\fR use \fBihr\fR(1) to obtain an irregularly sampled heart rate time
series.  \fBhrplot\fR plots this time series directly, and \fBhrlomb\fR uses
it as input to \fBlomb\fR, and then plots the spectrum.
.PP
All four programs accept the same \fIoptions\fR:
.TP
\fB-a\fR \fIannotator\fR
Read annotations from the specified \fIannotator\fR (default: the value of
the environment variable \fBANNOTATOR\fR, if set).
.TP
\fB-f\fR \fItime\fR
Begin at the specified \fItime\fR within the annotation file (default: the
value of the environment variable \fBSTART\fR, if set, or the beginning of the
file otherwise).
.TP
\fB-l\fR \fIaxes\fR
Log-transform the specified \fIaxes\fR (default: use linear axes).  The
\fIaxes\fR can be specified as \fBx\fR, \fBy\fR, or \fBxy\fR.
.TP
\fB-p\fR \fIplot-utility\fR
Use the specified \fIplot-utility\fR to generate the output (default: the
value of the environment variable \fBPLOT\fR, if set, or
\fBplt\fR(1), if it exists, or \fBplot2d\fR(1) otherwise). 
.TP
\fB-r\fR \fIrecord\fR
Produce a heart rate power spectrum for the specified \fIrecord\fR (default:
the value of the environment variable \fBRECORD\fR, if set).
.TP
\fB-t\fR \fItime\fR
Stop at the specified \fItime\fR within the annotation file (default: the
value of the environment variable \fBEND\fR, if set, or the end of the file
otherwise).
.TP
\fB-T\fR \fIdevice\fR
Produce output on the specified \fIdevice\fR (default: the screen).  The
\fIdevice\fR must be among those supported by the \fIplot-utility\fR (see
above).
.PP
If \fIannotator\fR or \fIrecord\fR are not specified using environment
variables or command-line options, these programs obtain values from the user
interactively.
.PP
Although \fBhrfft\fR, \fBhrlomb\fR, and \fBhrmem\fR all produce power spectra,
the units of power differ among them.  Absolute comparisons can be made only
between spectra produced using the same method, from time series of the same
length.
.PP
Note that these shell scripts can be run under MS-DOS using a suitable set
of UNIX-like utilities, such as the MKS Toolkit or the GNUish MS-DOS utilities,
and under MS-Windows using the free Cygwin package.
.SH ENVIRONMENT
In addition to the variables \fBANNOTATOR\fR, \fBEND\fR, \fBPLOT\fR,
\fBRECORD\fR, and \fBSTART\fR, it may be necessary to set \fBWFDB\fR
(see \fBsetwfdb\fR(1)).
.SH SEE ALSO
\fBfft\fR(1), \fBihr\fR(1), \fBlomb\fR(1), \fBmemse\fR(1), \fBplot2d\fR(1),
\fBplt\fR(1), \fBsetwfdb\fR(1), \fBtach\fR(1)
.SH AUTHOR
George B. Moody (george@mit.edu)
.SH SOURCES
http://www.physionet.org/physiotools/wfdb/psd/hrfft
.br
http://www.physionet.org/physiotools/wfdb/psd/hrlomb
.br
http://www.physionet.org/physiotools/wfdb/psd/hrmem
.br
http://www.physionet.org/physiotools/wfdb/psd/hrplot
